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Bug 1291252 - [doc] Documentation needed for how a VM syncs time with a Hypervisor
Summary: [doc] Documentation needed for how a VM syncs time with a Hypervisor
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: doc-Virtualization_Deployment_and_Administration_Guide
Version: 7.2
Hardware: Unspecified
OS: Unspecified
high
unspecified
Target Milestone: rc
: ---
Assignee: Jiri Herrmann
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2015-12-14 12:38 UTC by Laura Novich
Modified: 2021-08-30 12:53 UTC (History)
7 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2016-11-08 17:18:59 UTC
Target Upstream Version:
Embargoed:


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System ID Private Priority Status Summary Last Updated
Red Hat Knowledge Base (Solution) 27865 0 None None None 2016-09-29 01:26:33 UTC

Description Laura Novich 2015-12-14 12:38:20 UTC
Description of problem:
Requested by email on the virt-docs list from Anand Nande <anande>, customer support:

On 12/14/2015 05:02 PM, Anand Nande wrote:
> Hi,
>
> It would be great to have a brief article/doc in RHEL-7.x that 
> explains $subject along-with
> * timeline of events when the hypervisor and guest clock change 
> (time-drift)
> * how can they be adjusted back? OR how are they currently adjusted 
> using RH recommended best-practices
>
> Something on the lines of :
>
> more like
>
> host-NTP -> host-date -> host-hwclock
>         |            `-> guest-hwclock -> guest-date (boot)
>         `~> boot_ns [?] -> guest-kvmclock ~> guest-date (runtime)
>
>
> I have not seen this state diagram defined anywhere in our docs or 
> upstream.
> We can take help of Marcelo Tosatti [mtosatti] in this.
>
> Regards
> --Anand




Document URL: 

Section Number and Name: 

Describe the issue: 

Suggestions for improvement: 

Additional information:

Comment 1 Laura Novich 2015-12-14 12:39:54 UTC
consider making this a standalone article as well.

Comment 3 Laura Novich 2015-12-15 08:55:47 UTC
Incorporating email from Anand Nande
====================

Something like : http://www.ovirt.org/images/3/3e/StorageLiveMigrationAPIDiagram3.png would be a great idea.

Also we will need to consider the state diagram when the following conditions occur:

    Timer Drift

    Rounding Errors

    Suspend / Resume

    Migration


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